Residual gas entering high density hydrogen plasma: rarefaction due to rapid heating

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Abstract

The interaction of background molecular hydrogen with magnetized (0.4 T) high density (1-5 × 1020 m-3) low temperature (∼3 eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center, vibrational temperatures reached 1 eV. Rotational temperatures obtained from the Q(v = 1) branch were systematically ∼0.1 eV lower than the Q(v = 0) branch temperatures, which were in the range of 0.4-0.8 eV, typically 60% of the translational temperature (determined from the width of the same spectral lines). The latter is attributed to preferential excitation of translational degrees of freedom in collisions with ions on the timescale of their in-plasma residence time. Doppler shifts revealed co-rotation of the molecules with the plasma at an angular velocity an order of magnitude lower, confirming that the Fulcher emission connects to background molecules. A simple model estimated a factor of 90 rarefaction of the molecular density at the center of the plasma column compared to the residual gas density. Temperature and density information was combined to conclude that ion-conversion molecular assisted recombination dominates plasma recombination at a rate of 1 × 10-15 m3 s-1. The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy.

LanguageEnglish
Article number025020
Pages1-9
JournalPlasma Sources Science and Technology
Volume24
Issue number2
DOIs
StatePublished - 1 Apr 2015

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rarefaction
residual gas
hydrogen plasma
heating
temperature
molecules
corotation
plasma generators
gas density
angular velocity
line spectra
ions
estimating
degrees of freedom
collisions
shift
hydrogen
spectroscopy
excitation
interactions

Keywords

  • gas temperature
  • heating
  • hydrogen
  • molecular spectroscopy
  • plasma recombination
  • rotational temperature
  • vibrational temperature

Cite this

@article{69d74420300f48f4a7440b0cb0e7c493,
title = "Residual gas entering high density hydrogen plasma: rarefaction due to rapid heating",
abstract = "The interaction of background molecular hydrogen with magnetized (0.4 T) high density (1-5 × 1020 m-3) low temperature (∼3 eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center, vibrational temperatures reached 1 eV. Rotational temperatures obtained from the Q(v = 1) branch were systematically ∼0.1 eV lower than the Q(v = 0) branch temperatures, which were in the range of 0.4-0.8 eV, typically 60{\%} of the translational temperature (determined from the width of the same spectral lines). The latter is attributed to preferential excitation of translational degrees of freedom in collisions with ions on the timescale of their in-plasma residence time. Doppler shifts revealed co-rotation of the molecules with the plasma at an angular velocity an order of magnitude lower, confirming that the Fulcher emission connects to background molecules. A simple model estimated a factor of 90 rarefaction of the molecular density at the center of the plasma column compared to the residual gas density. Temperature and density information was combined to conclude that ion-conversion molecular assisted recombination dominates plasma recombination at a rate of 1 × 10-15 m3 s-1. The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy.",
keywords = "gas temperature, heating, hydrogen, molecular spectroscopy, plasma recombination, rotational temperature, vibrational temperature",
author = "{den Harder}, N.P. and D.C. Schram and W.J. Goedheer and {de Blank}, H.J. and {van de Sanden}, M.C.M. and {van Rooij}, {G. J.}",
year = "2015",
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Residual gas entering high density hydrogen plasma : rarefaction due to rapid heating. / den Harder, N.P.; Schram, D.C.; Goedheer, W.J.; de Blank, H.J.; van de Sanden, M.C.M.; van Rooij, G. J.

In: Plasma Sources Science and Technology, Vol. 24, No. 2, 025020, 01.04.2015, p. 1-9.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Residual gas entering high density hydrogen plasma

T2 - Plasma Sources Science and Technology

AU - den Harder,N.P.

AU - Schram,D.C.

AU - Goedheer,W.J.

AU - de Blank,H.J.

AU - van de Sanden,M.C.M.

AU - van Rooij,G. J.

PY - 2015/4/1

Y1 - 2015/4/1

N2 - The interaction of background molecular hydrogen with magnetized (0.4 T) high density (1-5 × 1020 m-3) low temperature (∼3 eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center, vibrational temperatures reached 1 eV. Rotational temperatures obtained from the Q(v = 1) branch were systematically ∼0.1 eV lower than the Q(v = 0) branch temperatures, which were in the range of 0.4-0.8 eV, typically 60% of the translational temperature (determined from the width of the same spectral lines). The latter is attributed to preferential excitation of translational degrees of freedom in collisions with ions on the timescale of their in-plasma residence time. Doppler shifts revealed co-rotation of the molecules with the plasma at an angular velocity an order of magnitude lower, confirming that the Fulcher emission connects to background molecules. A simple model estimated a factor of 90 rarefaction of the molecular density at the center of the plasma column compared to the residual gas density. Temperature and density information was combined to conclude that ion-conversion molecular assisted recombination dominates plasma recombination at a rate of 1 × 10-15 m3 s-1. The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy.

AB - The interaction of background molecular hydrogen with magnetized (0.4 T) high density (1-5 × 1020 m-3) low temperature (∼3 eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center, vibrational temperatures reached 1 eV. Rotational temperatures obtained from the Q(v = 1) branch were systematically ∼0.1 eV lower than the Q(v = 0) branch temperatures, which were in the range of 0.4-0.8 eV, typically 60% of the translational temperature (determined from the width of the same spectral lines). The latter is attributed to preferential excitation of translational degrees of freedom in collisions with ions on the timescale of their in-plasma residence time. Doppler shifts revealed co-rotation of the molecules with the plasma at an angular velocity an order of magnitude lower, confirming that the Fulcher emission connects to background molecules. A simple model estimated a factor of 90 rarefaction of the molecular density at the center of the plasma column compared to the residual gas density. Temperature and density information was combined to conclude that ion-conversion molecular assisted recombination dominates plasma recombination at a rate of 1 × 10-15 m3 s-1. The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy.

KW - gas temperature

KW - heating

KW - hydrogen

KW - molecular spectroscopy

KW - plasma recombination

KW - rotational temperature

KW - vibrational temperature

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JO - Plasma Sources Science and Technology

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SN - 0963-0252

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ER -